HIGHLY EFFICIENT, TIGHTLY REGULATED DC-TO-DC CONVERTER

• US 20040090801A1
• Filed: 11/13/2002
• Published: 05/13/2004
• Est. Priority Date: 11/13/2002
• Status: Active Grant

• Current Assignee: Tdk-Lambda Corporation (TDK Corporation)
• Original Assignee: TDK Innoveta Inc.
• Inventors: Chen, Qing, Lee, Victor Ke-Ji
• Granted Patent: US 6,728,118 B1
• Time in Patent Office: Days
• US Class Current: 363/24
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention presents a highly efficient, tightly regulated DC-to-DC converter which can be used in various applications, especially multiple output converters. The converter uses a buck converter to produce an intermediate bus voltage. A current-fed double ended circuit, such as bridge or push-pull circuit, couples to the buck converter to provide power to outputs. The double ended circuit operates at about 50% duty. The secondary output filter inductor is not required. With 50% duty cycle operation, the secondary rectifiers are easily controlled by either a self-driven or an external driven circuit. The secondary windings can also be stacked up to simplify the transformer design. In addition, bias voltages needed for control circuitry can also be obtained by adding extra windings to the power transformer and extra rectifier devices.

Claims

1. A dc-to-dc converter comprising:

(a) a buck converter having an input voltage and an intermediate bus voltage;

(b) a double-ended circuit in cascade through an inductor with the buck converter;

(c) a power transformer having a primary winding coupled to the double-ended circuit and two secondary windings;

(d) a first pair of rectifying diodes coupled to the first secondary winding and producing a first output voltage; and

(e) a second pair of rectifying diodes coupled to the second secondary winding and producing a second output voltage.

2. The dc-to-dc converter of claim 1 wherein the double-ended circuit is a full bridge circuit comprising two pair of switches, each pair operating at a fixed duty cycle.

3. The dc-to-dc converter of claim 2 wherein the fixed duty cycle comprises an approximately 50% duty cycle.

4. The dc-to-dc converter of claim 1 wherein the double-ended circuit comprises a first pair of switches operating out of phase with a second pair of switches.

5. The dc-to-dc converter of claim 2 wherein either pair of switches comprises a first switch on a first terminal of the primary winding a second switch on a second terminal of the primary winding.

6. The dc-to-dc converter of claim 1 wherein the double-ended circuit is a push-pull circuit.

7. A dc-to-dc converter comprising:

(a) a buck converter having an input voltage and an intermediate bus voltage;

(b) a double-ended circuit in cascade through an inductor with the buck converter;

(c) a power transformer having a primary winding coupled to the double-ended circuit and a plurality of secondary windings;

(d) a first pair of synchronous rectifier switches coupled to a first secondary winding;

(e) a second pair of synchronous rectifier switches coupled to a second secondary winding.

8. The dc-to-dc converter of claim 8 further comprises:

a synchronous rectification circuit having a drive winding coupled to the power transformer and coupled across the control terminals of the synchronous rectifier switch.

10. The dc-to-dc converter of claim 8 wherein the double-ended circuit is a full bridge circuit comprising two pair of switches, each pair operating at a fixed duty cycle.

11. The dc-to-dc converter of claim 8 wherein the double-ended circuit comprises a fixed duty cycle comprises an approximately 50% duty cycle.

12. The dc-to-dc converter of claim 8 wherein the double-ended circuit comprises a first pair of switches operating out of phase with a second pair of switches.

13. The dc-to-dc converter of claim 8 wherein a positive voltage across the control terminal of the synchronous rectifier switch turns the switch to an “

on”

state.

14. The dc-to-dc converter of claim 8 further comprises a first and second output circuits for producing a first and second output voltage and wherein each of said output circuits have a-pair of synchronous rectifier switches.

15. The dc-to-dc converter of claim 8 wherein the first pair of synchronous rectifier switches are out of phase.

16. The dc-to-dc converter of claim 8 wherein each synchronous rectifier switch is self driven.

17. The dc-to-dc converter of claim 8 wherein each synchronous rectifier switch is externally driven.

9. The dc-to-dc converter of claim 9 wherein the drive winding is coupled across the gate and source of a MOSFET.

18. The dc-to-dc converter of claim 9 wherein the double-ended circuit is a push-pull circuit.

19. A dc-to-dc converter comprising:

(a) a buck converter having an input voltage and an intermediate bus voltage;

(b) a double-ended circuit in cascade through an inductor with the buck converter;

(c) a power transformer having a primary winding and a secondary winding, wherein the secondary winding has multiple terminals;

(d) a pair of drive windings coupled to the power transformer; and

(e) a first pair of rectifier switches coupled between terminals on the secondary winding and the drive windings.

20. The dc-to-dc converter of claim 19 wherein the first pair of rectifier switches are out of phase.

21. The dc-to-dc converter of claim 19 further comprises:

a second pair of rectifier switches coupled between terminals of the secondary winding and the drive windings producing a second output voltage.

22. The dc-to-dc converter of claim 19 wherein the double-ended circuit is a full bridge circuit comprising two pair of switches, each pair operating at a fixed duty cycle.

23. The dc-to-dc converter of claim 22 wherein the fixed duty cycle comprises an approximately 50% duty cycle.

24. The dc-to-dc converter of claim 19 wherein the double-ended circuit comprises a first pair of switches operating out of phase with a second pair of switches.

25. A dc-to-dc converter comprising:

(a) a buck converter having an input voltage and an intermediate bus;

(b) a double-ended circuit in cascade through an inductor with the buck converter;

(c) a power transformer having a primary winding and a secondary winding, wherein the secondary winding has multiple terminals;

(d) a pair of drive windings coupled to the power transformer;

(e) a first pair of rectifier switches coupled between terminals on the secondary winding and the drive windings;

(f) a second pair of rectifier switches coupled between terminals on the secondary winding and the drive windings; and

(g) a bias voltage circuit coupled to the power transformer.

26. The dc-to-dc converter of claim 25 further comprises:

a second bias voltage circuit directly coupled to the drive winding.

27. The dc-to-dc converter of claim 25 wherein the bias voltage circuit comprises:

a bias voltage winding; and

a pair of rectifying devices

28. The dc-to-dc converter of claim 25 wherein the rectifying devices are rectifying diodes.

29. The dc-to-dc converter of claim 25 wherein the rectifying devices are rectifying switches.

30. The dc-to-dc converter of claim 25 wherein the double-ended circuit is a push-pull circuit.

31. The dc-to-dc converter of claim 25 wherein the double-ended circuit is a full bridge circuit comprising two pair of switches, each pair operating at a fixed duty cycle.

32. The dc-to-dc converter of claim 25 wherein the double-ended circuit is a push-pull circuit.